The invention relates to a roll shutter for roof windows of the casement-type construction, and more particularly to roll shutters which include a frame in which a storage shaft is rotatably arranged, two guide rails which extend parallel to one another and are disposed adjacent to the frame and a roll shutter draw mechanism. The guide rails are provided for the ends of the roll shutter bars, and include a crossbar which connects the guide rails with each other at ends thereof opposite the frame. The roll shutter draw mechanism includes two cords, one end of each of which is attached to the lower end of the roll shutter plating. The two cords are joined to a single common cord, which extends over stationary diverting elements to a drivable spool. The roll shutter mechanism also includes a length compensating device having a diverting element which is slidable against the force of an elastic member and over which the two cords are guided in tandem.
In a known roll shutter of this type (DE-OS No. 34 15 551), a holder is suspended on the elastic member, to support the movable diverting element. However, in this known apparatus, it is necessary to provide an elastic member which exerts a relatively large force in order to assure that, as the roll shutter plating is unwound from the storage shaft, the lower end of the roll shutter plating moves appropriately toward the crossbar without binding, even when subjected to differing conditions of friction.